1. Field of the Invention
The invention relates to an apparatus and process for the vaporization and filtration of liquid precursors and deposition of a film on a suitable substrate. More specifically, the invention relates to an apparatus and process for filtering precursors related to the deposition of a metal-oxide film, such as a barium strontium titanate (BST) film, on a substrate.
2. Background of the Invention
The increasing density of integrated circuits (ICs) is increasing the need for materials with high dielectric constants to be used in electrical devices such as capacitors for forming high capacity DRAMs. Capacitors containing high-dielectric-constant materials, such as organometallic compounds, usually have much larger capacitance densities than standard SiO2xe2x80x94Si3N4xe2x80x94SiO2 stack capacitors. Thus, the organometallic compounds are presently the materials of choice in IC fabrication.
One organometallic compound of increasing interest as a material for use in ultra large scale integrated (ULSI) DRAMs is BST due to its high capacitance. Deposition techniques used in the past to deposit BST include RF magnetron sputtering, laser ablation, sol-gel processing, and chemical vapor deposition (CVD) of metal organic materials.
A liquid source BST CVD process entails atomizing a compound, vaporizing the atomized compound, depositing the vaporized compound on a heated substrate and annealing the deposited film. The process requires a high level of control over the liquid precursors and gases from the introduction of the precursor from an ampoule into a delivery system which includes vaporization and ultimate delivery of the compound to the surface of the substrate where the compound is deposited.
A goal is to achieve a repeatable process which deposits a film of uniform thickness under the effects of a controlled temperature and pressure environment. However, this goal has not been satisfactorily achieved, because the BST precursors have a narrow range for vaporization between decomposition at higher temperatures and condensation at lower temperatures. Thus, the temperature controlled flow paths from the vaporizer into the chamber and through the exhaust system must be controlled relatively tightly. In addition, the precursors tend to form deposits in the delivery lines and valves disposed throughout the system.
Another difficulty encountered is the difficulty or lack of efficiency in vaporizing the liquid precursors. Typically, only a portion of the liquid precursors are vaporized due to low conductance in the vaporizer, thereby inhibiting deposition rates and resulting in processes which are not consistently repeatable. In addition, known vaporizers used in CVD processes incorporate narrow passages which eventually become clogged with unvaporized precursor during use and are not adapted for continuous flow processes which can be stabilized. The clogged passages result in a reduction in vaporization efficiency of the liquid precursors which negatively affects process repeatability and deposition rate. Still further, known vaporizers lack temperature controlled surfaces and the ability to maintain liquid precursors at a temperature low enough to prevent decomposition of the precursor prior to injection into the vaporizer. Thus, the lack of appropriate temperature control results in deposition of material in the injection lines in the vaporizer and premature condensation or unwanted decomposition of the precursors.
Therefore, there is a need for a deposition apparatus and method which can deliver liquid precursors to a vaporizer, efficiently vaporize and filter the precursors contemporaneously, deliver the vaporized precursors to the surface of a substrate and exhaust the system while maintaining elevated temperatures in the chamber, preventing unwanted condensation or decomposition of precursors along the pathway and avoiding temperature gradients in the system.
The present invention generally provides a deposition chamber for depositing materials which require vaporization, especially low volatility precursors, which are transported as a liquid to a vaporizer to be converted to vapor phase through one or more vaporizing elements and which must be transported at elevated temperatures to prevent unwanted condensation on chamber components. In one aspect, the chamber comprises a series of heated temperature controlled internal liners as vaporizing surfaces which are configured for rapid removal, cleaning and/or replacement and preferably are made of a material having a thermal coefficient of expansion close to that of the deposition material. The vaporizing surfaces xe2x80x9cflashxe2x80x9d sprayed liquid precursors on the surface of the vaporizing surfaces and then purify the flashed precursors before flowing further into the system. Particularly contemplated is an apparatus and process for the deposition of a metal-oxide film, such as a barium, strontium, titanium oxide (BST) film, on a silicon wafer to make integrated circuit capacitors useful in high capacity dynamic memory modules. Preferably, internal surfaces of the chamber are adjustable and maintainable at a suitable temperature above ambient, e.g., about 150xc2x0 C. to about 300xc2x0 C., to prevent decomposition and/or condensation of vaporized material on the chamber and related gas flow surfaces.
In one aspect, a gas feedthrough for a processing chamber comprises a conduit having an inlet and an outlet, the conduit defining a surface for forming a seal with the chamber, and a filter disposed in the conduit, said filter having a pore size and a surface area sufficient to prevent an excessive pressure differential to form across said filter.
In another aspect, a method of depositing a film comprises delivering one or more liquid precursors to a vaporizer, vaporizing the one or more liquid precursors, flowing the vaporized precursors through a gas feedthrough, and filtering the vaporized precursors in the gas feedthrough.
In another aspect, a vaporizer for a substrate processing system comprises an entry site for a liquid precursor, a perforated distributor surface sealably disposed around said precursor entry site for vaporizing said liquid precursor, an exit site for vaporized precursor, at least one filter disposed between said perforated distributor surface and said exit site, and a heating member thermally coupled to an interior of said vaporizer. In another aspect, a vaporizer for a substrate processing system comprises a body, a nozzle disposed in the body, and one or more vaporizing members disposed around said nozzle, having a porosity through which vaporized fluids pass of about 100 xcexcm or less.
In another aspect, a process chamber for depositing a film comprises a chamber body forming an enclosure having one or more temperature controlled surfaces, a lid movably mounted on the chamber body, said lid having a heated main body and an outer temperature-controlled collar and an annular gas feedthrough fluidicly coupled to said chamber and to a gas source, the feedthrough having a filter disposed therein, said filter having a pore size and a surface area sufficient to prevent an excessive pressure differential to form across said filter. In another aspect, a process chamber for depositing a film comprises a chamber body having one or more temperature controlled surfaces, a lid movably mounted on the chamber body, and a vaporizer. The vaporizer comprises an entry site for a liquid precursor, a perforated distributor surface disposed around said precursor entry site for vaporizing said liquid precursor, an exit site for vaporized precursor, at least one filter disposed between said perforated distributor surface and said exit site, and a heating member thermally coupled to an interior of said vaporizer.
In another aspect, a process chamber for depositing a film comprises a chamber body having one or more temperature controlled surfaces, a lid movably mounted on the chamber body, said lid having a heated main body and a temperature controlled collar, and a gas feedthrough fluidicly coupled to said chamber and to a gas source, said feedthrough having a filter disposed therein. In another aspect, a gas feedthrough for a processing chamber comprises a conduit having an inlet and an outlet, the conduit defining a surface for forming a seal with the chamber, and a filter disposed in the conduit. In another aspect, a process chamber for depositing a film comprises a chamber body having one or more temperature controlled surfaces, a lid movably mounted on the chamber body, the lid having a heated main body and a temperature controlled collar, and a vaporizer fluidicly coupled to the chamber body, the vaporizer comprising a nozzle disposed in the vaporizer and one or more vaporizing members disposed around the nozzle, the vaporizing members having a pore size of about 100 xcexcm or less.